A. Field of the Invention
This invention relates to apparatus and a method for processing and analyzing blood serum and more particularly to a system that automatically processes whole blood specimens to separate and withdraw the blood serum from the red blood cells and that also removes from further processing those specimens which are defective before the blood serum is withdrawn.
B. Description of Related Art
The process of separating the red blood cells from the blood serum of a whole blood specimen by centrifuge and then removing the blood serum is conducted on a large scale in hospitals and laboratories. This process is usually conducted manually by a technician. In the process, a stopper sealed test tube, containing a whole blood specimen and a separating gel, is centrifuged so that its contents are separated into three layers, a top layer containing the serum, a middle layer containing the separating gel, and a bottom layer containing the red blood cells. After the test tube is centrifuged, the technician must examine the blood specimen to determine whether it is defective. If the sample is not defective, the technician then inserts a needle through the rubber stopper, eyes the placement of the needle in order to insure the needle does not contact the separating gel, and withdraws a sample of the blood serum from the top layer and places the sample into a cup. Efficiency, accuracy, and maintaining the integrity of the blood specimen are essential to this process. More important is the safety of the technician while completing the process. By fully automating this process, these factors are greatly enhanced. The danger to the technician of being exposed to any transmitted diseases in the specimens during this process is eliminated.
U.S. Pat. Nos. 4,713,974 and 4,478,095 disclose devices for automatically piercing container lids and withdrawing samples. Neither of these patents disclose any means for sensing an appropriate level inside the test tube for positioning the tip of the sampling needle. Also, these patents do not disclose devices for use with centrifuged blood samples and do not disclose any means for automatically detecting defective samples.
U.S. Pat. Nos. 4,120,662 and 4,311,484 both disclose blood sample processing systems for delivering blood from closed vacutainers to a Coulter Counter. These systems are not suitable for use with centrifuged blood samples in that tubes are sampled in an approximately horizontal position and are agitated prior to sampling.
U.S. Pat. No. 4,326,851 discloses a level sensor for use with a fluid transfer mechanism for determining when the bottom tip of a fluid aspirating probe touches the top surface of a sample fluid. This device cannot be used with blood samples in conventional test tubes. In addition, the patent discloses no method or apparatus for automatically sensing whether the sample is defective.